The invention relates to improvements in papermaking machines, and more particularly to a positive locking foil blade mechanism wherein an improved foil blade structure and mount therefor is provided which positively positions the blade in operative position and permits removal thereof.
In a papermaking machine a traveling forming wire receives stock from the slice of the headbox with the stock being dewatered through the wire. One of the dewatering devices normally includes a foil which has an upper surface of soft or hardened material which is accurately positioned to form a diverging angle in the machine direction with the wire so as to cause an area of reduced pressure and help in dewatering the stock through the wire. It is imperative in the relationship between the foil blade and the wire that a uniform positional relationship be maintained with respect to the divergent angle of the foil relative to the wire. The foil blades wear with operation of the machine, and a typical arrangement permits removal of the foil blades and replacement with a reworked or fresh blade. Frequently, a T-bar support is provided which supports the blade and permits removal in a cross machine direction Typically, the tolerance between the conventional foil blade and the mounting T-bar is in the area of 0.008" to 0.20" loose. This loose fit tolerance between the foil blade and T-bar causes the blade to rock on the T-bar mounting, contributing to sheet rewet, dirt and fiber buildup on the blade with resultant possible worming or streaking of the paper sheet being produced. Also, deterioration of the paper formation from vacuum loss with the blade improperly positioned relative to the wire can occur. If tolerances are reduced, it becomes difficult or impossible for the papermaker to remove the blade from its position during operation. It is accordingly an object of the present invention to provide an improved foil blade mount which has a positive lock mechanism capable of tightly securing the loose fitting foil blade in an accurate operative position.
While the features of the invention find particular application in supporting a foil blade, it should be appreciated that the mounting structure can be utilized in mounting foils, deflector blades, forming board blades, blades for forming shoes and the like. For convenience the description will be presented with reference to a foil blade, but it will be understood that this is by way of description and not by way of limitation.
Another object of the invention is to provide a positive lock mechanism for a foil blade or other mechanism in close running relationship beneath a wire wherein a special holder is provided which is capable of holding the mechanism in a predetermined positive stop position during operation, and yet releasing the mechanism for easy and rapid removal for replacement.
Another object of the present invention is to provide an improved mechanism such as a foil blade and holder which can be locked during operation which offers advantages over structures heretofore available in that it is not difficult to keep clean, is not subject to weakening or deterioration of mechanical locking parts with continued operation, and is capable of adapting to the use of polyblades or ceramics or the use of additional adaptor parts without increasing down time for changes.
A still further object of the invention is to provide an improved support for foil blade or other mechanism and locking device therefor which is capable of very accurately locating the foil blade during operation and is capable to a degree of absorbing shaking and vibration of the foil during operation.
It is a feature of the invention to provide a foil blade mounted on a structured holder with the holder shaped to slide over a T-shaped mount. The mount is structured with a cross-machine slot fitted with an inflatable member therein which positions the holder rigidly relative to the mount during operation and which releases the holder for loose sliding relationship with deflation.